Means for actuating aircraft control surfaces



G. H. MILES 2,400,017 MEANS FOR ACTUATING AIRCRAFT CONTROL SURFACES May 7, 1946.

' Filed March 26, 1945 bodiment of the invention.

'vator I is movable in the ordinary way. For opermeme-i May 7',- 1946 2,400,017

MEANS FOR ACTUATING AIRCRAFT A CONTROL SURFACES George Herbert Miles, Reading, England, assign.

at tlo Miles Aircraft Limited, Reading, Eng- Application March 28, 1943, Serial No. 480,696 In Great Britain December 30, 1941 3 Claims. (Cl. 244-46) The present invention consists in safety means swings. The tab-actuating link i2, however, exfor limiting the control moment exertable by an tends forwardly. and is coupled to the bell-crank aircraft adjustable control surface comprising an. lever ll, itself swingable about a pivot ll. At its inertia-sensitivemass operatively associated with forward end the bell-crank lever I 4 carries an inafter described with reference to the accompanying diagrammatic drawing, of which:

Figure lshows schematically an arrangement according to the present invention;

Figure 2 corresponds to Figure 1 but shows the apparatus ina position in which the inertiasensitive mass has initiated a correction action, which in this instance may be regarded as applicable to elevator control when the associated aircraft is being pulled too violently out of a dive; while Figure 3 is a side elevation of a practical emmovement of it such as would result in operation of the tab 8 relatively to the elevator 5 until such time as the tab control weight is subject to predetermined excessive loads.

The invention will now best be understood with reference to the manner of operation and by comparison of Figure 2 with Figure 1. Thus, one can regard the position shown in Figure 1 as the norbe regarded that the aircraft is diving with its elevator set as shown in Figure 1 and the pilot Referring first to Figure 1, it can be regarded that the reference numeral 4 indicates the fixed tailplane surface with respect to which the eleshown in Figure 2, by which operation he puts wise about its axis and sets the elevator 5 upwardiy, as shown in Figure 2. Provided the moment which the elevator exercises to pull the aircraft out of its dive is not excessive having regard to the stress characteristics of the aircraft, the

tab will remain unaffected in regard to its relationship to the elevator I; but on the other hand if the pull-out is excessive to such an extent as to cause the tabcontrol weight It to swing the ating the elevator, the elevator has extending from it a-lever 8 which iscoupled by a link i to the pilot-operable control column 8. In thea'rrangement now under review, the tab 8 is provided at the trailing edge of the elevator 5. The tab 9 is in fact mounted so that it may move angularly with respect to the elevator ,being conplied elevator to be taken oif. V

"The point at which the tab 9 begins to be eilec tive is determined by the designer according to the nature of the machine with which he is concerned. Thus, on highly-manoeuvrable and fast combat aircraft adequately stressed, the tab 0 would probably begin to operate only under the influence of inertia loads on the weight It of the order of or 6 g., the arms I1 and II being loaded accordingly. For less highly-stressed aircraft the anticlockwise about the pivot. Likewise, if the tab 9 is moved anticlockwise it sets the elevator clockwise. A

Operation of thetab I is intended to be entirely automatic, and it will be observed that the tab 9 has a pivot Ill somewhat offset from the axis ii about which, the tabswings in relationhto the elevator; Connected to the pivot II is a tab-actuating link II which has a pivot connection i3 coincident with the axis about which the elevator 65 .wants to pull the craft out of '.its dive, he pulls; the control column I back towards the position the control surface to exert a reaction moment 5 automatic tab control weight it. Despite the tab tending to limit the control moment applicable by control weight Ii, the, bell-crank lever I4 is nora the control surface within safe limits having mally centralised'into a substantially horizontal regard to the stress characteristics of the airsetting by upper and lower loading arms I1 and craft. II, respectively. The upperloading arm I1 is Conveniently, the inertia-sensitive mass is,op=- 1o urged anticlockwise about its pivot is by any eratively associated with the control surface convenient form of torsion spring; while the lower through an auxiliary tab operatively associated loading am It is similarly urged clockwise about with the control surface. a -thepivot 20. The torsion springs are appro- In order that it may be clearly understood and priately chosen to achieve substantial balance of readily carried into eil'ect, the invention is herethe tab control weight in order to prevent any mal elevator setting for level flight. If now it the link i in tension, turns the lever B anticiocknected thereto in any convenient manner. .Tabs 40 bell-crank lever anticlockwise towards the posimounted on elevator and other main control surtion shown in Figure 2, the tab I is set upwardly faces (e. g. rudders. flaps and ailerons) are well in relation to the elevator 8, with the result that known; In practice, if the trimmer tab I is turned the effort applied through the control member I clockwise about the axis which connects it to the is opposed, in consequence of which there is at elevator Ii, it operates to swing the elevator 5 least a tendency for any excessive degree of apwith the tab 9 can be wholly enclosed within theano es? aircraft skin. Thus, if the anchorages for the loading arms Ill and it are naturally required to be disposed outside the profile of the fixed tailplane surface, then those anchorages can be arranged centrally so that the arms swing up and down in the plane of thefixed tail fin, the lower arm I! and its anchorage being if necessary within the tail end of the fuselage.

The arrangement shown in 1 and 2 would be equally effective against excessive inertia loads urging the weight l6 upwardly or downwardly.

Whereas in the arrangement shown with refer-'- ence to Figures 1 and 2 the moment exerted by the tab 9 under aerodynamic influence may mereively applied elevator is reduced to within predetermined safe limits.

The tab-actuating rod 28 is preferably enclosed by a fairing duct 80; while the teb-actuating levor 28 is similarly enclosed by the fairing 80.

The invention is not coed to its application to elevators, for it might very well operate ailerons to prevent over-stressing in exceptionally tight turns while, yet again, the invention may be usefully applicable to flap and rudder control. Although the safety means hereinbefcre described exemplify the invention as an arrangement in which the inertia-sensitive mass operates directly upon the tab, it may be desirable for the inertiasensitive mass to control a valve operating in turn to ensure the application of a progressive force to I the control system'or to the tab by means of a 1y serve to oppose the pull-out eifort applied by the pilot to give him adequate warning that he'is operating the control 8 too violently, it may be preferable to take oil any excessive application of elevator or similar control applied by the pilot automatically; although even then it may still be preferred to leave it possible for the pilot to override the safety control in extreme urgency.

Figure 3 illustrates an arrangement in which excessive applied'elevator control is immediately reduced or taken oil by operation of the tab. Thus in Figure 3 the elevator 5 is actuated entireiy by the tab 9. Therefore, to set the elevator 5 upwardly to lower the tail of the aircraft in relation to its flight path, the tab 9 is set downwardly, which operation swings the elevator 5 up about its mounting on the fixed tailplane, the trailing end of which is seen at 4 in Figure 3. To set the tab downwardly about its pivot axis on the elevator l, the tab-actuating lever 22 requires to be moved clockwise, and the tab-actuating rod 23 is therefore placed in tension by manipulation of the lack plunger 2| by pilot-operable control means (not shown). At its more rearward end the lack plunger is provided with a hook-shaped fitting 25 which mounts the pivot 2G. The forward end-of the tab-actuating rod 23 is not connected directly to the Jack but is coupled to the spindle 21 which interconnects two weighted arms laterally spaced one at each side of the hook fitting 2|; one of which arms is represented by the upon the weights 2!, as will inevitably occur if the pilot tends'to pull a fast and highly-manoeuvreble machine too violently out of its dive, the

weighted arms 28 swing downwards anticlockwise about the pivot 26. In other words, if it be assumed that the pilot attempts by manipulation of the tab 8 to set the elevator I upwardly to too great an extent, the weighted arms 20 swing down and so set the tail of the tab 0 upwardly in relation to the elevator, in consequence of which the fluid pressure system.

WhatIclaim is: 3

1. In aircraft including means defining a control surface adjustable in position to cause a change in the ,direction of movement of the aircraft and a tab pivotally mounted on the trailing edge of said means; a safety device comprising, means including a. pivotally mounted weight responsive to a predetermined rate of change of direction influenced by said control surface defining means for adjusting the angular position of said tab to'reduce the magnitude of the adjustment of the control surface defining means so as to hold the control moment exertable thereby within safe limits.

"edge of said means; a safety device comprising,

a weight plvotally mounted about an axis at right angles to the long axis of the aircraft for movement in response to those changes in aircraft direction influenced by said control surface defining means, a linkage connected to said tab for adjusting the angular position thereof in response to movement of said weight, the direction of movement of said weight controlling the direction of adjustment of said tab, and resilient means normally holding said weight in a position-corresponding to the normal flight position of said tab, said resilient means being loaded to yield to a predetermined inertia of said weight caused by a predetermined rate of change of direction of said aircraft whereby to cause adjustment of said tab to hold the control moment exertable by said control surface defining means within safe limits.

3. In aircraft including means defining a control surface and a tab pivotally mounted on the trailing edge thereof; a safety device comprising a pilot operatediack, a tab control rod for adjusting saidtab to effect servo control of said control surface defining means to thereby cause a change in the direction of movement of the aircraft, means including apivoted weight connectingthejack 'to the control rod, the position of the weight controlling the effective length of said rod. and resilient means normally holding said weight in a predetermined position, s id resilient means being ceded to yield to a predetermined inertia of said weight caused by a predetermined rate of change of direction of said aircraft whereby to modify the adjustment of said tab so as to hold the control moment exertable by said con- GEORGE HERBERT 

